X-ray Computed Tomography (CT) system can reconstruct a tomographic scanned image of an object utilizing computer technology, so as to obtain a three-dimensional (3-D) tomographic image. By transmitting a single axial plane radiation through an object under measurement, a computer acquires the penetrated radiation and generates an image by 3-D reconstruction based on the fact that the radiation absorptivity and transmittance by different parts of the object are different.
Currently, multiple scanning modes are exploited by a CT apparatus, where “step-scan” mode is widely used with the increasingly growing requirements of rotational speed, spatial resolution, width of a detector of the apparatus, and radiation dose. As for the step-scan mode, a certain number of Z position overlappings exist during two scanning processes according to specific requirements. In a practical scanning process, intermittent motions of a patient table may cause a patient move (such as cough, breathe or tiny shift), which results in inconsistence of images generated in different scanning processes, thereby affecting images' continuity and in turn adversely influencing medical diagnosis.